UMR 8640 : Photochimie Ultrarapide

Printer-friendly version

Discovery and Functional Analysis of a 4th Electron-Transferring Tryptophan Conserved Exclusively in Animal Cryptochromes and (6-4) Photolyases

 

A 4th electron transferring tryptophan in animal cryptochromes and (6-4) photolyases is discovered and functionally analyzed by transient absorption. It yields a much longer-lived flavin-tryptophan radical pair than the mere tryptophan triad in related flavoproteins, questioning the putative role of the primary light reaction of cryptochrome in animal magnetoreception.

Photo-induced cation translocation in a molecular shuttle based on a calix[4]-biscrown including DCM and DMABN chromophores

 

We present a new molecular shuttle, consisting of a calixarene core attached to two different photoactive centers, DCM and DMABN. We show that a K+ ion bound to the DCM-grafted crown is translocated towards the other site of the molecule upon photoexcitation, but not released to the bulk.

Real-Time Monitoring of Chromophore Isomerization and Deprotonation during the Photoactivation of the Fluorescent Protein Dronpa

 

Dronpa is a GFP-related photochromic fluorescent protein. It is known that the photochromic reaction involves cis/trans isomerization and protonation/deprotonation of the chromophore, but the sequence in time of the two steps and their characteristic timescales are much debated. We followed the entire photoactivation process of Dronpa in real time, by transient absorption spectroscopy from 100 fs to milliseconds.

 

Repair of the (6–4) Photoproduct by DNA Photolyase Requires Two Photons

It takes two (photons) to tango: Single-turnover flash experiments showed that the flavoenzyme (6–4) photolyase uses a successive two-photon mechanism to repair the UV-induced T(6–4)T lesion in DNA (see picture). The intermediate (X) formed by the first photoreaction is likely to be the oxetane-bridged dimer T(ox)T. The enzyme could stabilize the normally short-lived T(ox)T, allowing repair to be completed by the second photoreaction.

Spectro-Temporal Characterization of the Photoactivation Mechanism of Two New Oxidized Cryptochrome/Photolyase Photoreceptors

Nous avons étudié par spectroscopie d’absorption transitoire femtoseconde la dynamique de photoactivation de deux nouvelles flavoprotéines (OtCPF1 and OtCPF2) de la famille des cryptochromes et photolyase (CPF), issues de l’algue verte Ostreococcus tauri.